1. Field of the Invention
The present invention relates to a mobile track tamping machine arrangement comprising a first machine and a second machine, each machine comprising an elongated machine frame supported on undercarriages running on the track, a drive means for moving the machine frame in an operating direction along the track, the first machine preceding the second machine in the operating direction, and vertically adjustable track tamping tool units mounted on each machine frame, a detachable coupling connecting facing ends of the machine frames, a track leveling and lining unit operable to correct the track position, and a leveling and lining reference system controlling the operation of the track leveling and lining unit.
2. Description of the Prior Art
Such a mobile track leveling, lining and tamping machine arrangement has been disclosed in U.S. Pat. No. 3,744,428. This machine arrangement is comprised of two tamping machines which are linked together. Each machine is equipped with a tamping head for simultaneously tamping two successive ties so that four ties may be simultaneously tamped. To enable the two machines to operate independently, the coupling linking the machines to each other may be detached. This machine arrangement cannot be used for tamping track switches.
U.S. Pat. No. 4,947,757 discloses a switch tamping machine arrangement comprised of two tamping machines. One of the machines operates on the main track while the other machine operates on the branch track of the switch. The two machines operate in tandem and are connected by controls for synchronous operation of the track lifting units. The proper positioning of the two machines is time-consuming, and it has been found that the shorter ones of the long ties of the switch cannot be synchronously tamped because of a lack of space.
U. S. Pat. No. 3,494,297 discloses another type of track tamping machine arrangement comprised of two tamping machines linked together. It has no switch tamping capacity.
U. S. Pat. No. 5,031,542 discloses a tamping machine for use in tangent and switch track sections. For use in tamping long ties in switches, the machine has four transversely adjacently arranged tamping tool heads which are transversely adjustable independently of each other. The switch may be lifted in the area of the long ties by a track lifting unit and an auxiliary rail lifting device arranged for engaging a rail of the branch track.
U.S. Pat. No. 5,007,349 describes a tamping tool head with four transversely adjustable tamping tool units independently displaceable sideways beyond the machine frame by drives connected thereto.